Trans-Bishomobenzene

Lithiation of (425) results in carbene insertion and formation of bicyclobutane (426). This latter compound proves to be a valuable synthetic intermediate, affording trans-bishomobenzene (in 30-40 % yield, on a multigram scale) and homotropilidene (Scheme 66). Whereas (427), with no suitable C—H bond available for insertion,... 

A simple conversion of 3-norcarene into trans-bishomobenzene has been discovered. The method involves reaction of (693), itself obtained in two standard steps from 3-norcarene, with Bp3,OEt2. Silver perchlorate-catalysed decomposition of (693) gave 2,3-homotropilidene quantitatively. 

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